Statistics

Biochemistry

To calculate the molecular weight of nylon 6,6, we first need to understand its structure. Nylon 6,6 is a type of polyamide made from hexamethylenediamine and adipic acid. The repeating unit of nylon 6,6 can be represented as follows: \[ \text{[ - NH - (CH_2)_6 - NH - CO - (CH_2)_4 - CO - ]}_n \] Where \( n \) represents the number of repeating units in the polymer chain. To calculate the molecular weight of a single repeating unit of nylon 6,6, we need to sum the atomic weights of all the atoms in the unit. The molecular formula for the repeating unit is C12H22N2O2. Using the atomic weights from the periodic table: - Carbon (C): 12.01 g/mol - Hydrogen (H): 1.008 g/mol - Nitrogen (N): 14.01 g/mol - Oxygen (O): 16.00 g/mol Now, we calculate the molecular weight of the repeating unit: \[ \text{Molecular weight} = (12 \times 12.01 \text{ g/mol}) + (22 \times 1.008 \text{ g/mol}) + (2 \times 14.01 \text{ g/mol}) + (2 \times 16.00 \text{ g/mol}) \] \[ \text{Molecular weight} = (144.12 \text{ g/mol}) + (22.176 \text{ g/mol}) + (28.02 \text{ g/mol}) + (32.00 \text{ g/mol}) \] \[ \text{Molecular weight} = 226.316 \text{ g/mol} \] The molecular weight of a single repeating unit of nylon 6,6 is approximately 226.316 g/mol. The significance of the molecular weight in polymer science is multifaceted: 1. **Mechanical Properties**: The molecular weight of a polymer is directly related to its mechanical properties such as tensile strength, toughness, and elasticity. Higher molecular weight polymers generally have better mechanical properties because of the increased number of entanglements between chains. 2. **Thermal Properties**: The melting and glass transition temperatures of a polymer can be influenced by its molecular weight. Higher molecular weight can lead to higher melting and glass transition temperatures. 3. **Processability**: The molecular weight affects the viscosity of the polymer melt. High molecular weight polymers are more viscous, which can make them more challenging to process. 4. **End-Use Applications**: Depending on the application, specific molecular weights will be targeted to achieve desired properties. For example, fibers like nylon 6,6 for textiles may require a different molecular weight than nylon used for engineering plastics. 5. **Solubility and Miscibility**: The solubility of a polymer in solvents and its miscibility with other polymers can be influenced by its molecular weight. Lower molecular weight polymers tend to be more soluble and have better miscibility with other materials. In summary, the molecular weight of nylon 6,6 is a critical parameter that affects its physical, mechanical, and processing properties, which in turn determines its suitability for various applications in polymer science and industry.

Question

Calculate the molecular weight of nylon 6,6 and discuss its significance in polymer science.

Solution

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